Reviews can only be given on a machine supplied. Logically you would be unable to give a review on customer service as this is completely subjective would be totally unworkable.
For example, I have bought over 80 laptops, peripherals and desktops from PCWorld. On the few occasions that I have had to return an item I have always had exemplary service and courtesy. I do not expect Sun systems level advice, when you are paying £5.80 an hour you are not going to get top level experts and like when buying a car I do my own research as it is not rocket science. However there are some that write that they have had atrocious service...maybe they got a service rep having a bad day or maybe their attitude left a bit to be desired. It is obvious that any company wants to keep it's customers happy as they will return, so no company actively aims for bad service.
OTOH I have witnessed some appalling morons and knuckle draggers berating shop staff and if I were in their shoes I would have chinned the customer into next week.
So, in conclusion, I would thoroughly recommend PCW but I'll bet that there are some that think they are the devil incarnate....so how would you assess customer service? It is also worth remembering that you only hear one side of a story when someone reports 'bad service', they are usually unable to give an objective report. A cou[ple of years ago there was a poster on another forum who created merry hell because a now defunct computer company refused to supply him with a computer. He complained about their appaling service and lack of customer care. In the end it turned out that he had sent three 'bad' cheques. They had tried to be reasonable but he lost it. Even after this he was still posting that he was the victim. Naturally I'm not saying that this happens in every case but you only hear one side and you are not privy to conversations.